The number of people diagnosed with autism could be reduced by nearly a third under new diagnostic criteria for the developmental disorder, researchers say.

Last May, a new edition of the Diagnostic and Statistical Manual of Mental Disorders, known as the DSM-5, introduced sweeping changes to the criteria for an autism diagnosis. The update did away with Asperger’s syndrome, childhood disintegrative disorder and pervasive developmental disorder, not otherwise specified, instead establishing an umbrella classification of “autism spectrum disorder” with clinicians indicating a level of severity.

Now, a study published in the Journal of Autism and Developmental Disorders is adding to worries that some who previously would have qualified for a diagnosis on the autism spectrum will be left out.

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Researchers found that 31 percent of those who met the diagnostic criteria for autism under the old DSM may no longer meet the new standards. Without a diagnosis, children may not qualify for needed services, researchers said.

“We are potentially going to lose diagnosis and treatment for some of the most vulnerable kids who have developmental delays,” said Kristine Kulage of the Columbia University School of Nursing who led the study. “In many instances, children require a diagnosis of ASD to receive medical benefits, educational support and social services.”

Kulage and her colleagues reviewed more than 400 previously published studies to assess the impact of the changes in the updated DSM. They found that the number of children who will be diagnosed with autism under the new criteria will “significantly decrease” as compared to the old definition.

What’s more, in cases where children no longer qualify for an autism diagnosis, the researchers said that some also will not meet the criteria for social communication disorder — a new condition in the DSM-5 designed to account for those with communication difficulties but no other autism symptoms.

“This study raises a concern that a medical provider diagnosing a child under the new guidelines won’t find the child to be on the autism spectrum, when the same child under the old criteria might have been diagnosed with ASD,” Kulage said.

The study is just the latest to raise alarm bells about changes to the way autism is defined. Earlier this year, researchers looking at surveillance data from the U.S. Centers for Disease Control and Prevention found that nearly 1 in 5 children previously diagnosed with autism would not qualify under the new definition.

Even before the updated DSM was finalized, many advocates voiced concerns. That led those behind the revision to insert language into the autism definition stipulating that anyone with a “well-established” diagnosis of autistic disorder, Asperger’s or PDD-NOS under the old DSM should be considered to have autism spectrum disorder going forward.